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Interlisp.maiko/NEWCDRCODING.md
Nick Briggs ce28b0da56 Add documentation of NEWCDRCODING cdr codes
2020-09-16 15:12:58 -07:00

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The cdr-code is a 4-bit field of a 32-bit cons cell. It is treated as an on-page indicator bit and a 3-bit scaled offset.

Certain combinations are treated specially.

on-page offset interpretation
1 0 CDR is NIL
1 1 - 7 CDR is at 2*offset (counted in 32-bit cells) on same page
0 0 CDR is indirect, CDR(car)
0 1 - 7 CDR is not a cons cell but is in the car of cell at 2*offset on same page
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